An angle is made up of two rays that begin at a common point.
A ray is part of a line. It has an endpoint and goes on forever in some direction.
The vertex is the common endpoint of the arms of the angle.
A right angle is exactly 90°.
A right angle is marked by drawing a square at the vertex.
By putting two right angles together, we can create a square.
A lot of things around us are made up of right angles.
Just like this window and this book.
Can you think of other things that have the right angles?
An angle that is less than 90° is called an acute angle.
Acute means "sharp". If you have an acute pain, it's a sharp pain.
If you see a sharp angle like the ones below, it's surely an acute angle.
Angles that measure 10°, 20°, 45°, and 70° are all acute angles.
If it's less than 90°, then it's an acute angle.
These things are made up of acute angles.
An angle that is greater than 90° but less than 180° is called an obtuse angle.
Tip: The word obtuse can describe someone who is slow to learn, or not that sharp.
This can help you remember that obtuse angles are not that sharp.
Angles that measure 91°, 100°, 140°, and 170° are some examples of obtuse angles.
Just don't start calling your family members obtuse. 😂
A straight angle is exactly 180°.
A straight angle forms a straight line.
An angle greater than 180° and less than 360° is called a reflex angle.
Great job learning about the five types of angles.
Now, complete the practice. It'll help you remember for longer.